• How kubernetes hides away the volumeMounts complexity

    4 min read

    volumeMounts overlay kubernetes

    If we try compare volumeMounts with the actual mounts that we have on a pod using, for example, df it can be quite confusing due to the usage of the overlay filesystem

    Let's consider the volumeMounts section of a deploy:

    $ kubectl get deploy pet2cattle -o yaml (...)  volumeMounts:  - mountPath: /opt/pet2cattle/conf  name: config  - mountPath: /opt/pet2cattle/data  name: pet2cattle  subPath: data  - mountPath: /opt/pet2cattle/lib  name: pet2cattle  subPath: lib  - mountPath: /tmp  name: tmp-dir (...)

    And compare it with the filesystem we see on the pod:

    $ kubectl exec pet2cattle-8475d6697-jbmsm -- df -hP Filesystem Size Used Avail Use% Mounted on overlay 100G 9.7G 91G 10% / tmpfs 64M 0 64M 0% /dev tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroup /dev/xvda1 100G 9.7G 91G 10% /tmp shm 64M 0 64M 0% /dev/shm /dev/xvdcu 20G 2.5G 18G 13% /opt/pet2cattle/lib tmpfs 3.9G 12K 3.9G 1% /run/secrets/kubernetes.io/serviceaccount tmpfs 3.9G 0 3.9G 0% /proc/acpi tmpfs 3.9G 0 3.9G 0% /proc/scsi tmpfs 3.9G 0 3.9G 0% /sys/firmware

    13/04/2021

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From pet to cattle
Treat your kubernetes clusters like cattle, not pets